I wanted to update my fireplace with slate but didn't want the pre-fab versions found on line and in stores. I purchased 12X12 slate tile from Home Depot and another unnamed source and cut 1.5" strips with my wet saw. WHAT A MESS! but it was well worth it. By using the tile, I was able to choose color pattern and width/length of strips. I had to first cover the concrete blocks with cement backer-board and used modified thin set to adhere tile. Even though the slate is much darker than the original 1966 era concrete block, the fireplace looks a lot larger now. It's truly a focal point in the room. I love the way it turned out!
Now I'm making a new faux reclaimed box-beam mantel. I'll upload a photo when it's completed.